The present invention concerns an analogue display watch with a first time display for a first time zone, associated with a first time-setting device, a second time display for a second time zone, associated with second, manual, time-setting means, and a time zone indicator including at least one index and a place ring for the places representing the time zones. The place ring rotates opposite said index, or vice-versa, the first, manual time-display means are able to set the time of the first and second time displays simultaneously, and the second time-setting means are able to rotate the second time display and the time zone indicator together, step by step, without changing the state of the first time display.
A description of a watch of this type can be found in U.S. Pat. No. 3,633,354 (=DE 1933049). In the version of FIGS. 1 and 2 of that patent, the time display includes four central hands, including a seconds hand and a minute hand, which are driven, as usual, by the watch movement. Via a conventional motion work, the cannon-pinion drives a 24-hour wheel carrying a first hour hand, for indicating, for example, the home time, on a 24-hour scale. To display the time of the second time zone, generally the local time, a second hour hand is secured to a 12 hour wheel, which is connected to the 24-hour wheel by a planetary gear, whose planetary wheel carrier carries the place ring that bears the city names appearing in turn in an aperture of the dial, to identify the second time zone. A conventional time-setting device with a stem and crown rotates the 24-hour wheel and 12 hour wheel simultaneously, and thus the two hour and minute hands. A second time-setting device, activated by a manual crown or push-buttons, moves the planetary wheel carrier by steps of 1/24th of a revolution, and thus the place ring and simultaneously the 24 hour wheel and its hand.
With this construction, when the same time is displayed by both hour hands, it is always the same time zone (the original one) that is indicated by the place ring. If one wished the user to be able to change the original time zone, one would have to add a device for disconnecting the two hour hands. Moreover, with the concentric display of two different times, the user is liable to misread the display.
The change from winter time to daylight saving time and vice versa also raises a problem when this does not occur at the same time in both of the time zones concerned, since the time difference between the two time displays has to be specially altered, while keeping the same place indication. In particular, this problem arises each time that one of the two places considered is in the northern hemisphere and the other is in the southern hemisphere. Thus, for this reason too, it is desirable to have time-setting or correction means that offer greater freedom of manipulation, while allowing the usual manoeuvres to be carried out as simply as possible.
An additional problem with this type of watch is due to time zones whose time difference relative to coordinated universal time (UTC) is not an integer multiple of an hour. For example, the official time of some countries or territories is set with steps of a half-hour (for example in India, Iran, Newfoundland, Venezuela etc.), or a quarter-hour (Nepal), relative to the 24 conventional time zones. It is thus desirable to be able to indicate the time in such time zones using the second time display, without the user being forced to perform more complicated manipulations than for a conventional time zone. A rudimentary system was provided, in U.S. Pat. No. 4,717,260, which allows time differences of half an hour in a universal time watch, but it could not be used for a dial with two time displays.
Because of the aforementioned problems, it is only practical to use most current watches that display two time zones in some standard situations and it becomes too complicated in other cases.